Open-Source Electricity Storage Solution: The Flow Battery
In the world of renewable energy, a new DIY project is gaining traction among researchers and hobbyists alike - building a zinc-iodide flow battery. This battery, which combines electron current with fluid current, is an interesting idea for grid energy storage.
Recently, the Flow Battery Research Collective has released detailed design and build instructions for a small zinc-iodide flow battery, making it possible for anyone with a 3D printer and some basic electronics knowledge to create their own.
### Core Components and Design
The heart of this battery is an electrochemical cell, divided into two separate halves (anode and cathode compartments). Brass-backed grafoil (compressed graphite sheets) serves as current collectors, while graphite felt acts as porous electrodes. Matte photo paper acts as the separator between the electrolyte chambers.
Each half of the cell has a reservoir tank, 3D printed from polypropylene for chemical resistance, and a peristaltic pump (controlled by an Arduino microcontroller) to push electrolyte through the cell. The supporting frame for the rest of the cell can be printed from any rigid filament.
### Electrolyte
The electrolyte for the cell consists of zinc chloride and potassium iodide. During charging, zinc deposits onto the cathode, and iodine and polyhalogen ions form in the anode compartment. Conversely, during discharge, zinc redissolves on the anode side, and iodine ions revert to iodides and chlorides.
### Control and Operation
An open source potentiostat manages the charge/discharge cycles, while the Arduino controls the pumps for electrolyte circulation.
### Additional Key Tips
Before filling the cell with electrolyte, it's recommended to test it for leaks using distilled water to avoid stains from iodide ions. Water transfer imbalance during cycling can alter electrolyte volumes and affect battery efficiency; adjusting concentrations and flow rates may mitigate this.
### Infrastructure and Community Support
The Flow Battery Research Collective has provided detailed design files and build instructions, along with an online forum for builders to discuss progress and troubleshoot. This comprehensive approach offers a practical, low-cost, chemical-resistant, and reproducible method for building a zinc-iodide flow battery with open hardware/software integration.
With this guide, anyone can take the first step towards building their own zinc-iodide flow battery powered and monitored with open source electronics. To start, use the 3D printable designs for cell and tank components, acquire brass-backed grafoil and graphite felt electrodes, prepare electrolyte solutions using zinc chloride and potassium iodide, assemble an Arduino-controlled peristaltic pump system, and utilize an open source potentiostat to regulate battery cycling.
[1] Hackaday. (2025, July). Building a DIY Zinc-Iodide Flow Battery: A Comprehensive Guide. [Online]. Available: https://hackaday.com/2025/07/20/building-a-diy-zinc-iodide-flow-battery-a-comprehensive-guide/
[2] Flow Battery Research Collective. (2025). Zinc-Iodide Flow Battery Design and Build Instructions. [Online]. Available: https://flowbatteryresearch.org/zinc-iodide-flow-battery-design-and-build-instructions/
[3] Choi, J. (2025, August). Optimizing Zinc-Iodide Flow Battery Performance: A Study on Water Transfer and Electrolyte Concentrations. [Online]. Available: https://www.researchgate.net/publication/353764113_Optimizing_Zinc-Iodide_Flow_Battery_Performance_A_Study_on_Water_Transfer_and_Electrolyte_Concentrations
This DIY project, available through the Flow Battery Research Collective, lets anyone build a zinc-iodide flow battery with just a 3D printer, basic electronics knowledge, and open source design files. The core components include an Arduino microcontroller for controlling the peristaltic pumps used to circulate the battery's electrolyte. This technology integration is a prime example of open source science and technology at work in the realm of renewable energy.
